A social networking service is an online service, platform, or site that focuses on facilitating the building of social networks or social relations among people who may share interests, activities, real-life connections, or backgrounds. A social network service consists of a representation or profile for each user, his/her social links, and a variety of additional services. Most social network services are web-based and provide a way for users to interact over the internet, such as e-mail and instant messaging. Social networking sites allow users to share ideas, activities, events, and interests within their individual networks. Popular social networking services include Facebook™, Google+™, Twitter™, LinkedIn™, YouTube™, Foursquare™, Yelp™, Expedia™, MySpace™, and Flickr™. An individual may use many social networking sites, each which enable the individual to interact with other users via countless social network communications, or network feeds. A social networking system can be an enterprise social networking system used within an enterprise or a public social networking system open to the public. Enterprise social networking systems are increasingly becoming a common way to facilitate communication among people, any of whom can be recognized as users of a social networking system.
Several types of events can occur within the social network. The events can be related to a feed item of a social networking feed or to any other changes within the social network. For example, the events can be actions performed by one or more users on a feed item, such as reading a feed item, posting a feed item, commenting on a feed item, or indicating a personal preference such as “likes” and “dislikes,” updates to a user's status, uploaded files, and user-submitted hyperlinks to social network data or other network data such as various documents and/or web pages on the Internet. In a social network feed several events may occur in relation to one or more feed items. In another example, the events can be items on which an action is performed, such as a feed item that is commented on, read, deleted, etc. In another example, the events can represent the creation of new items or entities in the social network, such as the creation of a group, a feed item, a user, etc. Other examples of changes or updates within the social network that occur at a given time can be considered an event.
Determining the number of unique events that occur during a period of time is challenging as the same event can occur several times during that period. For example, attempting to determine the unique number of users that performed an action on a feed item during an interval of time will have a large performance cost, as each user can perform the same action several times during that interval of time.